The present invention relates to an injection syringe for medical purposes, having a syringe cylinder and at least one displaceable syringe plunger, the cylinder having a needle attachment piece at one end thereof, and at an opposite end thereof an aperture for filling and for introducing the syringe plunger or plungers.
The syringe should, in particular, offer the possibility of drying medicine within the syringe in a vacuum or lyophilizing (freeze-drying) of the same. During freeze-drying, considerable quantities of solvent are drawn off in the vacuum, which means that the container in which the substance to be treated is contained, must have sufficiently large apertures through which the solvent vapor can escape.
Syringes of this type are known from European Patent Applications Nos. (examined) 0,191,122 and 0,144,483, and No. DE-OS 33-39-705. In these references, a solution to the above-noted problem which is suggested is a type of syringe which has a large aperture at its needle-side end which is only closed after the completion of the lyophilizing process by inserting a needle attachment piece.
A disadvantage in these syringe types, is that enclosing the finished lyophilized substance in the syringe takes place by inserting the needle attachment piece. In this process, several parts must be assembled for which elaborate technical operations are required which must be carried out in the sterile area of the production installation, since the syringe may only leave the sterile area when the lyophilized substance is tightly enclosed in the syringe.